Scleroderma or systemic sclerosis (SSc) is a multi-system disease with high morbidity and mortality whose etiology and pathogenesis are unknown. The pathological picture in SSc includes widespread cutaneous and visceral fibrosis, obliterative small vessel disease, and autoimmune phenomena. Increasingly, evidence is being accumulated that SSC is a complex and heterologous in which several (or many) genes interact, perhaps also with environmental factors. Identification of these genes using conventional family-based genome wide scans is made difficult by the rarity of SSc and its infrequency of familial recurrence. In this project, however, a relatively isolated and inbred human population has been identified (Choctaw Native Americans) in which SSc occurs with high frequency and displays clinical homogeneity. Having genealogically traced the origins of the affected Choctaw to common founders, microsatellite and single nucleotide polymorphism (SNP) mapping strategies in candidate gene regions are being used to identify genes relevant to SSC in this population (with extension to other ethnic groups in Project 3). Evidence is presented that fibrillin-1 (FBN1), SPARC (or osteonectin) and the MHC are genetically associated with SSC, while a large number of other candidate genes have been excluded. A genome-wide scan in the in the Choctaw using over 400 microsatellite markers and LD mapping strategies to confirm and identify candidate regions for genetic fine mapping is currently being conducted. In addition, cDNA microarrays are being used to examine gene expression in SSC fibroblasts is currently being conducted. In addition, cDNA microarrays are being used to examine gene expression in SSC fibroblasts, so as to better understand molecular pathogenesis and identify relevant genes. Thus, the overall aims of the project remain the same, namely the justification of genes predisposing to SSC susceptibility and expression. Specific aims are as follows: 1) to perform genetic fine mapping of candidate genes/regions using SNPs at high density (300 kb) with genetic analysis performed using LD mapping and case-control methods; 2) genes identified in #1 will then be tested using SNPs and SNP haplotypes in the Project 3 SSc cohort (GENISOS) of unrelated, ethnically-defined but diverse, and clinically well- characterized SSc cases, as well ethnically-matched normal controls, to determine their impact on disease susceptibility and/.or clinical and/or serological expression, and outcomes; 3) to define and compare gene expression profiles using cDNA microarrays in SSc dermal fibroblasts and other tissue (muscle, peripheral blood mononuclear cells) vs their normal counterpart tissues, especially in the context of known biochemical pathways; and, 4) explore whether SSC serum factors, especially specific autoantibodies, can induce SSC-like gene expression changes (seen in microarrays) in normal fibroblasts and endothelial cells, the likely primary target tissues resulting in the scleroderma phenotype. The relatively inbred and isolated Choctaw population with its extraordinary high prevalence of SSc, the well-characterized GENISOS cohort and the application of newer gene technology (SNPs and arrays) combine to afford a unique opportunity to discover genes relevant to SSC.